1. Field of the Invention
The present invention relates to a probe assembly for inspecting power semiconductor devices and an inspection apparatus for power semiconductor devices using the probe assembly.
2. Description of the Related Art
For inspecting electric characteristics of power semiconductor devices, such as power transistor and IGBT (Insulated Gate Bipolar Transistor), it is preferable as a matter of course to apply large electric current at a level of several hundreds amperes to the device under test adapting to its actual operating conditions. However, when a large electric current is applied through inspection probes to a power semiconductor device in wafer state or in chip state after dicing, the semiconductor device and/or the inspection probes generate heat because of internal resistance of the semiconductor device and contact resistance found at the contact points of electrodes of the semiconductor device and the probes. The heat thus generated tends to invite temperature drift which disturbs accurate measurements, and damage the semiconductor device and/or inspection probes in some cases.
In view of the circumstances as above mentioned, power semiconductor devices are, in general, roughly selected in wafer state or in chip state by inspecting their characteristics applying relatively small electric current to them, and then finally inspected in the final process after having been assembled in a package. However, characteristic faults are frequently found in a final full-spec inspection on some of the power semiconductor devices which passed characteristics inspections conducted by applying small electric current. In that case, various processes carried out after the rough selection become useless, which invites disadvantages such as products cost rising and waste volume increasing.
On the other hand, as to probe cards, many types of probe cards equipping a cooling means have been proposed. The Japanese Patent Kokai Hei 2-192749 (JP1990/192749 A1), for example, discloses a probe card which has a cooling pipe inside of the probe card to flow an appropriate cooling medium. The cooling means, however, is equipped in the probe card not to prevent probes or a semiconductor device from being heated by large electric current applied to the semiconductor device through the probes, but to prevent the probe card from melting or deforming by the heat radiated from a semiconductor device which is heated at high temperature for inspection.
The Japanese Patent Kokai No. 2000-28641 (JP2000/28641 A1) discloses a probe card, which supplies cooling air to a cooling chamber to cool the base part of probe needles contained in the cooling chamber, thereby preventing the heat transfer from a semiconductor device heated at high temperature for inspection to the probe card. In this probe card, however, what is in question is not the heat generated in the semiconductor device or in the proves by large electric current applied to the semiconductor device for inspection through the probes, but the heat transferring from the semiconductor device under test to the probe card. In addition, the probe card has disadvantages that the cooling effect is not sufficient because the base part of the probe needles are cooled just by cooling air which come into contact with the outer surface of the base part.
Further, the Japanese Patent Kokai No. 2007-121245 (JP2007/121245 A1) discloses a probe card, which has Peltier elements attached to the side wall of a ceramic board which composes the probe card, and leading wires branched from a part of the probe wires which are connected to the side wall of the ceramic board. The probes are cooled through the leading wires. The probe card, however, has disadvantages that the cooling effect may not be sufficient because the probes are cooled indirectly through the leading wires. Furthermore, since the probe card needs the leading wires to cool the probes, the structure of the probe card is complicated and a lot of works is needed to produce the probe card.
The present invention was made in view of the conventional technical situation as above mentioned. An aim of the present invention is to provide a probe assembly for power semiconductor devices, which makes it possible to realize accurate measurements by effectively preventing temperature rising caused by electric current supplied to the probes and the semiconductor device in a large current inspection of power semiconductor devices. Another aim of the present invention is to provide an inspection apparatus for power semiconductor devices, which uses the probe assembly for power semiconductor devices.